Low-k dielectric (“LKD”) films are used in the semiconductor industry for reducing interconnect delay in integrated circuits (“ICs”) versus tradition dielectric materials. Dielectric materials used in ICs include inorganic materials such as silicon dioxide (“SiO2”), which has a k-value of about 4.0. Other dielectric materials include spin on dielectric films and LKD films obtained from spin coating, dip coating, spray coating, chemical vapor deposition (“CVD”), rolling, dripping, and/or spreading. Generally, LKD materials having k-values below 3.0 are desirable.
Lower k-values in inorganic materials can be achieved by adding carbon to reduce polarizability, thereby reducing the k-value. Ultra-low k-values (i.e., <2.4) can be achieved by adding porosity to the LKD materials. Such porous LKD materials are prone to collecting impurities because the film interior is exposed through the pores.
LKD materials can get damaged during plasma etching, resist ashing, and/or cleaning operations of the ICs. During etching, ashing, and/or cleaning operations, at least a portion of carbon containing moieties can be removed resulting in LKD materials having reduced hydrophobicity. When the carbon containing moieties are removed from the LKD materials Si—C bonds are replaced with Si—OH (“silanol”) bonds or groups and the resulting dielectric layer loses its hydrophobicity as water molecules from the atmosphere form strong hydrogen-bonding interactions with the silanol groups. The presence of water which has a k-value of about 70 results in a significant increase in the k-value of the LKD material.
Further, porous LKD materials tend to form voids after copper annealing due to high tensile stress which destroys device yields.
Therefore, there is a need for repairing damaged LKD materials such that k-values can be restored along with restoring the mechanical integrity of the damaged LKD materials.